On Tue, Oct 23, 2012 at 8:58 AM, Jakub Jelinek <ja...@redhat.com> wrote: > On Tue, Oct 23, 2012 at 08:47:48AM -0700, Xinliang David Li wrote: >> > + /* The builtin below cannot be safely instrumented as their >> > + length parameter is just a mere limit. >> > + >> >> Why can't the following be instrumented? The length is min (n, strlen (str)). > > Because that would be too expensive, and libasan intercepts (most of the) > str* functions anyway, both so that it can check this and test argument > overlap. The memory builtin instrumentation is done primary for the cases > where the builtins are expanded inline, without calling library routine, > because then nothing is verified in libasan. >
Ok that makes sense. thanks, David >> For 'strlen', can the memory check be done at the end of the string >> using the returned length? > > Guess strlen is commonly expanded inline, so it would be worthwhile to check > the shadow memory after the call (well, we could check the first byte > before the call and the last one after the call). > > Jakub
